bpo-42111: Make the xxlimited module an example of best extension module practices (GH-23226)



- Copy existing xxlimited to xxlimited53 (named for the limited API version it uses)
- Build both modules, both in debug and release
- Test both modules
diff --git a/PC/layout/main.py b/PC/layout/main.py
index 3eef755..8c69c915 100644
--- a/PC/layout/main.py
+++ b/PC/layout/main.py
@@ -36,7 +36,7 @@
 BDIST_WININST_FILES_ONLY = FileNameSet("wininst-*", "bdist_wininst.py")
 BDIST_WININST_STUB = "PC/layout/support/distutils.command.bdist_wininst.py"
 
-TEST_PYDS_ONLY = FileStemSet("xxlimited", "_ctypes_test", "_test*")
+TEST_PYDS_ONLY = FileStemSet("xxlimited", "xxlimited_35", "_ctypes_test", "_test*")
 TEST_DIRS_ONLY = FileNameSet("test", "tests")
 
 IDLE_DIRS_ONLY = FileNameSet("idlelib")